Questions 51 to 55 are based on the following passage.Twenty years ago, the Urban Land Ins

Questions 51 to 55 are based on the following passage.

Twenty years ago, the Urban Land Institute defined the two types of cities that dominated theUS landscape: smaller cities that operated around standard 9-5 business hours and largemetropolitan areas that ran all 24 hours of the day. Analyzing and comparing cities using thelens of this basic divide gives interesting context to how investment capital flows and housingprices have shifted.

In recent years, many mid-sized cities have begun to adopt a middle-of-the-road approachincorporating the excitement and opportunity of large cities with small cities&39; quiet aftermidnight. These 18-hour cities are beginning to make waves in real estate rankings and attractmore real estate investment. What is underlying this new movement in real estate, andwhy do these cities have so much appeal？

18-hour cities combine the best of 24-hour and 9-5 cities, which contributes to downtownrevitalization. For decades, many downtown cores in small to mid-sized cities were abandonedafter work hours by workers who lived in the suburbs. Movement out of city centers waswidespread, and downtown tenants were predominantly made up of the working poor. Thisgenerated little commerce for downtown businesses in the evenings, which made business andgenerating tax revenue for municipal upkeep difficult. With the rise of a new concept in urbanplanning that aims to make life easier and more convenient, however, increasing popularityfor urban areas that cased the real estate pushes, in major cities like San Francisco or NewYork, has inspired a type of forward thinking urbanity and in smaller cities.

Transforming downtown areas so that they incorporate modern housing and improvedwalkability to local restaurants, retail, and entertainment—especially when combined withimproved infrastructure for cyclists and public transit—makes them appeal to a more affluentdemographic. These adjustments encourage employers in the knowledge and talentindustries to keep their offices downtown. Access to foot traffic and proximity to transit allowthe type of entertainment-oriented businesses such as bars and restaurants to stay openlater, which attracts both younger, creative workers and baby boomers nearing retirementalike. Because of their smaller size, most keep hours that allow people to enjoy themselves, then have some quiet after midnight, as opposed to large major cities like New York, wherethe buzz of activity is ongoing.

These 18-hour cities are rapidly on the rise and offer great opportunities for homeownerinvestment. In many of these cities such as Denver, a diverse and vigorous economyattracted to the urban core has offered stable employment for residents. The right urban mixhas propped up home occupancy, increased property values, and attracted significantinvestment capital.

What do we learn about American cities twenty years ago？

A.A.A.They were divided into residential and business areas.

B.B.B.Their housing prices were linked with their prosperity.

C.C.C.There was a clear divide between large and small cities.

D.D.D.They were places where large investment capital flowed.

What does the passage say about kola nuts？

A.A.A.Their commercial value was first discovered by Portuguese settlers.

B.B.B.They contain some kind of energy boost not found in any other food.

C.C.C.Many were shipped to Europe in the late 19th century for medicinal use.

D.D.D.They were strange to the Europeans when first imported from West Africa.

Years ago, many downtown cores in small to mid-sized cities.

A.A.A.had hardly any business activity

B.B.B.were crowded in business hours

C.C.C.exhibited no signs of prosperity

D.D.D.looked deserted in the evenings

What characterizes the new downtown areas in 18-hour cities？

A.A.A sudden emergence of the knowledge industry.

B.B.Flooding in of large crowds of migrant workers.

C.C.Modernized housing and improved infrastructure.

D.D.More comfortable life and greater upward mobility.

What have 18-hour cities brought to the local residents？

A.A.More chances for promotion.

B.B.Healthier living environment.

C.C.Greater cultural diversity.

D.D.Better job opportunities.

请帮忙给出每个问题的正确答案和分析，谢谢！